Consider the following statements regarding soils : 1. Soils having a very high content of sodium and calcium and pH of more than 7·0 are alkaline soils. 2. Black cotton soil had developed on the Deccan basaltic lava under hot and humid conditions. 3. Laterite soils are characterised by a deep weathered layer from which silica has been leached. Which of the statements given above is/are correct ?

Statement 1 is incorrect: Alkaline (sodic) soils are characterised by a high proportion of exchangeable sodium and a high pH (often > 8.0). However, they typically have a low content of soluble calcium, because calcium precipitates out as calcium carbonate at high pH levels. In fact, adding calcium (via gypsum) is the standard treatment to reclaim alkaline soils.

Statement 2 is correct: Black cotton soil (Regur soil) is formed from the weathering of Deccan basaltic lava. The chemical decomposition of the parent volcanic rock into fine clayey soils was facilitated by hot temperatures and sufficient moisture (interpreted in this context as humid/sub-humid conditions).

Statement 3 is correct: Laterite soils develop in areas with high temperatures and heavy rainfall. This climate causes intense leaching (desilication), washing away silica and leaving behind a deeply weathered layer rich in iron and aluminium oxides.

Therefore, only statements 2 and 3 are correct.